Transcript Air Masses and Fronts

Air Masses and Fronts
Types of air masses
• An air mass is a huge body of air that has
similar temperature, humidity and air
pressure throughout it.
• There are four major types of air masses
that influence the weather in North
America: maritime tropical, continental
tropical, maritime polar and continental
polar.
Maritime Tropical Air Mass
• Warm humid air masses that form over
oceans near the tropics.
• In the summer, maritime tropical air
masses bring hot, humid weather.
• In the winter, maritime tropical air masses
bring heavy rain or snow.
Maritime Polar Air Masses
• Cool humid air masses form over the icy
cold North Pacific and North Atlantic
oceans.
• These masses of cool humid air bring fog,
rain and cool temperatures to the West
Coast.
Continental Tropical
• Hot dry air masses form only in the
summer over dry areas of the Southwest
and Northern Mexico.
Continental Polar Air Masses
• Form over central and northern Canada
and Alaska.
• Continental polar air masses bring cold or
cool air.
• In winter, continental polar air masses
bring clear, cold, dry air to North America.
How Air Masses Move
• Air masses move because of the major
wind belts pushing them along.
Do Now:
What is a front?
Fronts
• As huge masses of air move across the
land and the oceans, they bump into each
other but they do not mix.
• Where the two air masses meet and do
not mix is called a front.
• You will find storms and changeable
weather at fronts
Types of fronts
• There are four types of fronts: cold fronts,
warm fronts, stationary fronts and
occluded fronts.
• The kind of front that develops depends on
the characteristics of the air masses and
how they are moving.
Cold Front
• A cold front forms
when fast moving
cold air mass runs
into a slowly moving
warm air mass. The
cold air mass forces
the warm air mass up
causing clouds, rain
or snow. Cold fronts
are also known for
thunderstorms.
Warm Front
• Warm air mass
collides with cold air
mass causing the less
dense warm air to
rise. If the warm air is
humid, this collision
causes clouds and
rain. If the warm air is
dry, this collision
causes scattered
clouds.
Stationary Front
• Cold and warm front
meet but neither are
able to push the other
out of the way. At the
front, clouds, fog and
rain develops. If a
stationary front
remains stalled over
an area, it may bring
many days of clouds
and precipitation.
Occluded Front
• In an occluded front, a
warm air mass is
caught between two
cooler air masses.
The warm air is forced
up as the denser cool
air pushes into the
area. The weather
gets cooler and can
cause clouds and
precipitation.